Hydraulically operated compressors



Dec. 23, 1958 o. .1. SCHEMMEL 2,365,553

HYDRAULICALLY OPERATED COMPRESSORS Original Filed Jan. 22, 1954 y .53 WSTON OING DOWN l jzve1it7 or/ 0H0 I Dchemmel,

United States Patent HYDRAULICALLY OPERATED COMPRESSORS Otto J. Schemmel, Chicago, Ill.

2 Claims. (Cl. 230-49) This invention relates to improvements in hydraulically operated compressors, and the like. More specifically, the compressors herein disclosed are intended for the compression of refrigerants used in refrigerating operations, such as for the refrigerating of enclosed spaces for the storing or preservation of such materials as meats and other edibles, chemicals requiring cooling and refrigerating conditions, and many other similar uses.

The present improvements concern themselves with the provision of means to produce and deliver to hydraulically motor-operated compressors the motive liquid under pressure suitable for operation of the compressor units, and specifically, the provision of such means for use on refrigerated trucks and like conveyances.

A principal object of the invention is to provide a highly efiicient, compact compressor unit, and to provide such a unit with a dual system of supply of motive liquid under pressure, whereby such hydraulically operated compressor unit may be operated by the motive liquid under pressure supplied by either of two definitely related sources of pressure liquid supply. Both of such supply sources of pressure liquid are so interconnected and related to each other that change-over from either one to the other may be effected automatically and without special attention to the change-over operations by the truck driver, and yet with assurance that in either form of operation the supply of pressure motive liquid will be certainly delivered to the compressor unit. Thus, there will be assurance that the desired refrigerating action will proceed without interruption, even when such changeover is effected.

' At this point the following comments are pertinent for the purpose of facilitating a better understanding of the the student to a realization of the importance of such ope'rations, and of the inter-relationship between the various elements comprising the dual system of motive power liquid pressure supply herein disclosed:

Refrigerated trucks of that type in which the refrigerating operation is produced by the use of the heat cycle, necessarily include in their equipment power driven compresso'rs for compressing and liquifying the refrigerant which is then cooled by suitable means such as air radiators, and thereafter expanded in the expansion unit to produce the refrigerating action. The present invention concerns itself especially with an improved form of such power driven compressor. The arrangement is such that during normal operation on the road the power needed to run such compressor is derived from the power plant of the refrigerated truck. It is however, highly desirable to be able to operate the refrigerating compressor to produce the desired cooling effect while the truck motor is idle. This occurs notably when the truck is laying over for extended intervals at terminals or at delivery or loadingstations. In many cases, also, it is desirable to-pre-cool the refrigerated space prior to loading, so

7 2,865,558 Patented Dec. 23, 195s ice that time may be saved after the loading operation has been completed, or, in some cases to refrigerate the loaded space prior to starting the travel of the truck with its load. In all such cases the needed refrigerating action is produced while the truck motor is standing idle.

When provision is made only for operation of the refrigeration compressor by power derived from the trucks power plant it is evident that it is necessary to keep the trucks power plant in operation during such lay over or loading or unloading intervals. Since the amount of power needed for operation of the refrigerating compressor is only a-small percent of the capacity of the trucks power plant it is evident that the operation of the trucks power plant motor only for the refrigerating action, and for extended intervals of time, is a highly ineflicient and consequently expensive operation. Additionally it would entail needless operation and wear of the trucks power plant. The operation of the internal combustion engine of the trucks power plant while standing within an enclosed space, such as a station or terminal, also presents elements of danger to health, as well as fire hazards, etc.

It is also noted that when the truck is of that type including a so-called tractor unit to which the truck body is removably connected during normal road running, the detachment of such body from the tractor unit, as is customary during extended layovers, makes the tractor power plant unavailable as a source of power for refrigeration at such times. v

To meet the foregoing and like conditions, it has been a widely adopted practice to drive the refrigerating compressor by a small specially provided internal combustion engine. Such arrangements present many objections from installation as well as operational standpoints. The use of electric motor drives for such truck refrigerating compressors, using current from the trucks storagebattery has been proposed. This scheme, however presents the serious objection that operation of the refrigerating compressor by battery current alone, for an extended interval of ten of fifteen hours, or more, in a terminal station entails the provision of battery capacity far beyond the normal requirements for truck operation, with corresponding high first cost and the need of carrying a very large dead load during truck travel. It is also pointed out that even should it be decided to use such electric motor drive for the refrigeration compressor, operating it off of the usual truck power motor driven electric generator during normal road running operations, such electric motor compressor can not be directly fed with electricity from the available electricity service supplies at the terminals in order to avoid operation off of the trucks battery. This is true since the usual truck battery and electrical equipment are designed for six or twelve volt or similar low voltage D. C. operation, whereas the usual electricity services are of either or volt A. C. rating.

Accordingly it is a prime object and feature of the present invention to provide a refrigeration compressor unit and system of operation which is admirably adapted to meet the normal road running operating conditions of the refrigerated truck, as well as the very special contojsuchpumping source. During normal road operation the pressure and return oil lines are connected to a specially provided oil driven motor which is driven by the trucks power motor, as by a beltdrive from the fan belt shaft; or, alternatively, such pressure and return oil lines may be connected to the pressure and return sides of the oil pump of the trucks power engine itself. In case of provision of such special oil pump it may be readily accommodated under the engine hood. I then also provide a supplementary electric motor driven .oil pump, having its pressure and return-oil lines connected to the pressure and return oil .lines for the oil driven refrigerant compressor, under proper valve control so that the refrigerant compressor may be operated by pressure oil supplied either by the .trucks engine oil circulatmg system and returned to such system for re-circulation, orby such special belt driven pump, for normal road running conditions; or so that the refrigerant compressor may be operated by pressure oil supplied by such electric motor driven oil pump and returned to such pump for repeated re-circulation. Such supplementary electric motor driven oil pump may be provided with an electric motor of the A. C. type, intended for operation on the usual 110-115 volt A. C. service supply which is almost always available at the loading or unloading station or wharf.

By my novel arrangement outlined above it is possible to use the power supply available in the conventional form of truck power plant for normal road operation, and substantially without change of costly or objectionable nature. It is also possible to change over to lay over refrigerating operation by merely plugging an electric line from the supplementary electric motor driven oil pump into any available service outlet socket .at the terminal or other layover point.

The valve control above referred to includes check valves in the lines, so placed and arranged that when either of the sources of pressure oil is being used for supply of motive liquid to the compressor unit such pressure oil so supplied by such unit will not 'by-pass through the other, non-used source of supply, but will be blocked off therefrom, permitting the pressure oil, however, to reach the oil motor element of the compressor unit for drive of the same. This valve arrangement is also such that change-over from either source of pressure oil supply to the other source will be effected automatically when the substitute source of supply is brought into operation, thusallowing the former source of supply to then be discontinued in its operation, or to merely cease supplying the pressure oil to the compressor unit. By this arrangement, when a truck equipped with my improved system of refrigeration reaches its destination or point of considerable time stop the electric motor unit may be plugged into the available electric service socket and brought up to speed, thus commencing supply of the pressure oil to the compressor unit. Thereupon the power motor of the truck may be stopped, or the tractor unit be disconnected fromthe refrigerated truck body, all without cessation of the operation of the refrigerating operations. Thereafter, when the truck is ready to move away from its point of delay, its powermotor may be brought into operation, taking the supply of pressure oil into its function, whereupon the electric motor driven unit may be unplugged and the truck will be ready to move away to its next scheduled point. disclosed means to etfect all of the foregoing operations, as well as others.

Other objects and uses of the-invention will appearfrom a detailed description ofthe same, which consists in the features of construction and combinations of parts driven by the trucks power motor, a second oil pumping v:

I have herein element driven by an electric motor, pressure supply and return oil lines connecting both such pumping elements to the pressure oil driven motor element of the compressor unit, and check valves in the oil lines between the two pumping elements and the pressure oil driven motor element to ensure automatic change-over operations according to one feature of my present invention;

Figure 2 shows schematically one form of pressure oil driven refrigerant compressing unit which may be used in connection with the presently disclosed system of operation; and

Figure 3 shows in perspective a conventional form of truck provided with elements comprising the inventive features hereinbefore referred to, to enable automatic change-over from either form of pressure oil pump operation and supply, to the other form thereof.

This application is a division of Serial No. 405,599, filed January 22, 1954, now Patent No. 2,791,370, issued May 7, 1957. In that earlier application I have shown a form of hydraulically operated compressor and have claimed the same. In order to better understand the operational conditions to meet which the present system of generation and supply of hydraulic liquid under pressure has been devised, I shall first describe briefly the form of compressor unit which is shown in that earlier parent application, and shall then describe the hydraulic pumping and supply system to which the present divisional application is particularly directed.

The form of hydraulically operated compressor of that earlier parent application is schematically shown in Figure 2 of the present case. Such compressor unit includes the two vertically reciprocable pistons 23 and 24 working in suitable cylinders, and these pistons are connected to compressor elements in the form of movable walls of compressing chambers. Such movable Walls may be either pistons or other elements such as diaphragms. They need not be herein illustrated in detail as such devices are well known in the compressor arts. As each of the pistons 23 and 24 is forced up its companion compressing wall is moved to compress a charge of vapor, discharging the compressed vapor to the proper outlet. When each of the pistons 23 and 24 is moved down its companion compressing wall is oppositely moved to draw into the compressing chamber a new charge of vapor which will thereafter becompressed on the contrary stroke of such piston. The hydraulic motor or driving element shown in Figure 2 serves to thus reciprocate these movable walls of the compression chambers. It remains to show how the two pistons 23 and 24 are alternately forced up for the vapor compressing function, and then allowed to move down for the vapor indrawing operation, and how these functions are effected automatically by the hydraulic pressure medium supplied by the present system of production and supply of the hydraulic pressure medium.

The oil or other hydraulic medium is supplied to the unit of Figure 2 through the line 66 and is afterwards discharged from such unit through the line 66. A main valve 44 is provided in the unit of Figure 2, which main valve is reciprocable through a range of movement sufiicient to change certain port connections in the manner required for effecting the operations of the pistons 23 and 24. Supply and discharge conduits 59 and 58, respectively connect the cylinder of the piston 24 with the enclosure wherein such main valvereciprocates; and supply and discharge conduits 56 and 57, respectively connect the cylinder'of the piston 23 with such en-= closure wherein such main valve reciprocates. This main valve is reciprocated by a control valve element'53, an

intermediate gear element 49 being meshed with suitable teeth carried by both the control valve element and the main valve. Such control valve element works back and forth in a suitable cylindrical enclosure, the

conduits .86 and 9]. connecting into the cndportions of such cylindrical enclosure. By introducing pressure medium into one end. of such enclosure behind the proximate end of the control valve element such valve element is driven towards the other end of the enclosure, the conduit of that end being then connected to a release passage to allow the medium contained behind that end of the control valve element to discharge. Conversely, by reversing the supply and release of the pressure medium to the two conduits 86 and 91, the control valve element will be driven back again to its original positions. Thus, by alternately introducing pressure medium into and releasing such medium from the two ends of the enclosure of the control valve element such valve element is driven back and forth, carrying with it the main valve 44.

Pressure liquid conduits 61 and 64 connect to the enclosure of the main valve 44 in alignment with the conduits 56 and 59 which reach from the main valve enclosure to the cylinders of the pistons 23 and 24, respectively. The main valve element is provided with crosswise extending ports 46 and 47 which are spaced apart properly to produce the following operational functions:

With the main valve in its position shown in Figure 2 the pressure liquid conduit 61 is connected through the valve port 46 to the conduit 56 leading to the cylinder of the piston 23 and at the same time the discharge conduit 58 for the cylinder of the piston 24 is connectedthrough the valve conduit 47 to an opening of the main valve enclosure to allow discharge of liquid from such cylinder of the piston 24. Thus the piston 23 is driven up and at the same time the piston 24 is allowed to move down. Upon reversing the main valve by reciprocation to the right the valve port 46 will establish connection of the conduit 57 with the discharged liquid space, and the valve port 47 will establish connection of the conduit 59 with the pressure liquid conduit 64. Thus the operations of the two pistons will be reversed, the piston '24 moving up and the piston 23 moving down. In the embodiment shown in said parent application I have provided mechanical interconnections between" the two pistons so that their reciprocations shall be mechanically compelled to synchronize with each other, the one moving down a full stroke while the other moves up a full stroke. It is not deemed necessary to illustrate such means herein as devices of such nature and functions are well known in the pumping arts.

Two primary valves are provided for controlling delivery of pressure liquid to the conduits 86 and 91 which actuate the reciprocations of the control valve 53 and for release of liquid from behind the ends of such 5 control valve to allow movement of such valve under the urge of pressure liquid so delivered by such primary valves. These primary valves are designated 77 and 77 in Figure 2. They include the chambers 120 and 121 forthe two primary valves, respectively. The pressure liquid supply conduit 66*- connects to these chambers by the conduits 122 and 123, respectively; and the pressure supply liquid conduits 61 and 64 also connect into such chambers 120 and 121, respectively. The valve elements which work in these chambers do not control connection of the pressure liquid supply conduits 122 and 123 with the corresponding conduits 61 and 64, but pressure liquid connection is always established between the conduits 122 and 61, and between the conduits 123 and 64, respectively, the chambers merely constituting convenient connections between such pairs of conduits without, cross connections between such pairs.

The conduits 86 and 91 connect into the chambers 120 and 121, respectively; but valve seats 124 and 125 areprovided in such chambers between the conduits 122 and 61, and the conduit 86, on the one hand, and between the conduits 123 and 64, and the conduit 91, on the other hand. The poppet valves 77 and 77 are adapted to seat against such valve seats to thus seal off the cofi duits 8 6 and 91 from the corresponding pressure liquid' conduits 122 and 123, respectively; and springs 69 and 69 urge the poppet valves to their seats. The valve stems 79 and 87 extend from the poppet valves through the ends of the corresponding chambers, to locations where, by pressing against such stems the poppet valves may be forced back against their springs 69 and 69*, re-

spectively, to thus momentarily establish connection between each of the conduits 86 and 91, and the correthat when the corresponding valve element 77 or 77? is seated against the seat 124 or,125 (as is the case with the right-down valve element in Figure 2), connection is established from the conduit 86 or 91, as the case'may be, to the correspondingrelease conduit 83 or 83. On

the other hand, when each of the stems 79 or 87, as the case may be, is forced inwardly by pressure against its projecting end to unseat the corresponding valve element 77 or 77 with corresponding connection of the conduit 86 or 91 with the conduit 122 or 123, as the case may be,

such conduit 86 or 91 is sealed off from the corresponding conduit 83 or 83 so that the pressure liquid will not be allowed to discharge through such conduit 83 or 83* at such time. Thus pressure will be properly developed against the desired end of the control valve to effect operation of the main valve. r

The inward pressing of the valve stems 79 and 87 in proper timing with the up and down movements of the pistons 23 and 24 is effected by lugs or the like connected to such pistons in position to etTect such inward pressing of the valve stems in proper timing at conclusion of the piston strokes. For purposes of schematic showing I have, in Figure 2, shown such lugs at 81 and 88 connected to the pistons 23 and 24, respectively. The lug 81 is there shown in engagement with the valve stem 79 to depress the valve element against the spring 69 according to the functions already explained. The result of such depression is that pressure liquid is being admitted to the left-hand end face of the control valve 53 which has thus been shifted rightwardly into the position shown. Thus the two main valve ports 46 and 47 have been brought into positions to admit pressure liquid to the pis-' ton 23, and to allow release of liquid from; beneath the piston 24. Such relationship will continue until the positions of the pistons have been reversed and the lug 88 brought into engagement with the valve stem 87, it being noted that the engagement of each lug 81 or 88 with the companion valve stem is maintained for only a short interval of time, sufiicient to ensure shift of the position of the control valve 53.

From the foregoing it will be understood that pressure liquid supply to the line or conduit 66 with provision for release of liquid from the line or conduit 66 will ensure proper operation of the compressor unit for com- I pression of the refgrigerating vapor.

Referring now to Figures 1 and 3, I have shown the compressor unit by the numeral 110. At 1131 have shown a liquid pumping unit connected to an electric motor 115, and at 114 I have shown another liquid pumping unit connected to the belt drive 117 by means of the pulley 116. Each of these pumping units is of form capable of delivering motive liquid under pressure needed to effect operation of the compressor unit 110, suchpressure being sufficient to ensure compression of the refrigerating medium or vapor to that pressure needed for the operation of the heat cycle for refrigeration purposes. Thejpressure liquid delivery connections of both pumping units 113 and 114 are connected together by the line 111, to which line isconnected the pressure liquid conduit 66 of the unit 110, it being understood that such unit 110 responds generally to the compression functions produced by the unit shown in Figure 2, and previously described herein. The liquid supply connections for both pumping units 113 and 114 are connected together by the line 112, to which line is connected the liquid release conduit 66 from the unit 110.. In the line 111 there is located the check valve 126 between the pumping unit 113 and the connection 66 to the compressing unit 110; and in the line 111 there is located the check valve'127 between'the pumping unit 114 and such connection 66 to such compression unit 110. Both of these check valves are so set into such line 111 that flow of liquid is permitted only in the directions indicated by the arrows adjacent to such check valves. The pressure deliveryconnections of the two pumping units 113 and 114 are connected to such line 111, and the two return or supply connections of the two pumping units are connected to the line 112.

, Examination of this Figure 1 will now show that when either of the pumping units 113 or 114 is being driven at ptoper speed it will supply pressure liquid through the adjacent check valve and along the line 111 to the supply conduit 66 leading to the compressor unit 110; but it will also be seen that neither of the pumping units 113 or 114 can deliver pressure liquid to such other pumping unit, since such liquid movement reversely into such other pumping unit is forbidden by its proximate check valve. From this it is also evident that when using either pumping unit for supply of motive pressure liquid to the compressor unit no back fiow of such pressure liquid to the other pumping unit can occur even when such other pumping unit is idle. Neither can pressure liquid from either pumping unit be delivered into the other pumping unit when both units are operating at the same time, but one'is delivering a higher pressure than the other. Thus it appears that transfer of the supply of pressure liquid to the compressor unit 110 may be effected from either of the pumping units which may be delivering pressure liquid to the compressor unit, to the other pumping unit. This may be done by merely bringing the idle pumping unit up to pressure delivering speed, and then reducing the speed of the other pumping unit. Thus the load may be transferred from one pumping unit to the other whenever desired and without the need of any manual control or operation of any valve in the liquid supply and delivery lines.

In Figure 3 I have shown a convenient and desirable form of installation of my improved refrigerating system on a truck of conventional form. In this showing the compressor unit 110 is carried by a forwardly extending bracket or shelf on the front wall of the truck body according to conventional practice. The motor driven pumping unit may be carried by a side bracket or running board installation as shown, so that during lay-over interva'ls the motor of such pumping unit may be readily connected toan available electric service supply outlet by a conventional cord and plug arrangement. The belt 117 which rides the pulley 116 of the pumping unit 114 may be conveniently driven by the fan drive of the trucks power motor, or other convenient point of power takeoff from such power motor.

1 wish to point out that when the refrigerated truck is equipped with the herein described means for provision of thec'ompressed refrigerating medium all requirements for operation of such refrigeration system both when on the'road, and when laying over at a terminal or other delay point, are met, and that all that is necessary when w changing from road running condition to layover condition-is to plug in the electrical'supply cord of the motor driven pumping unit 115 into a convenient'outletandturn unit now being taken automatically'by the motor driven pumping unit withoutneed of further operationsby'the truck. driver or other person. Contrarily, when the truck is tobe'again taken ontothe road it is only necessary'to bringthe trucks power'motor up to speed, and then disconnect the electric supply cord from the outlet. Thus there is substantially no danger of improper operations by an inexperienced driver when transferring from the one form of operation totheother, and at the same time continuity of refrigerating operation is assured both prior to and after transferringthe power source, and also during the act of making such transfer.

I claim:

1. The combination'with a motor driven truck having a refrigerated bodyenclosure inwhich use is made of a compressible fluid refrigerating medium, of means to cornpress the'refrigerating fluid medium comprising a unit includinga pressure liquid operated motor and a fluid compressor in driven connection with said motor, said pressure liquid operated motor being provided with pressure liquid supply and release liquid connections for supply of pressure liquid to the'liquid operatedmotor arid delivery of released liquidifrom said motor, together with means to place the liquid under pressure, said pressure liquid means including first and second liquid pumping units each having a pressure liquid delivery connection and a return liquid intake connection, the first liquid pumping unit being mounted in proximity to the power motor of the truck, means to drivingly connect a, power driven element of the'power motor to the first liquid pumping unit, an electric motor, means to drivingly connect said electric motor to the second. defined liquid pumping unit, means to supply. electric'currenttojsaid electric'motor, a common pressure liquidiconduit connecting together the pressure liquid delivery connections of the first and second liquid pumping units, a common return liquid conduit connecting together the return liquid intake connections of the first and second liquid pumping units, a pressure liquid supply conduit connecting the common pressure liquid conduit aforesaid to the pressure liquid supply connection of the liquid operated motor, a return liquid conduit connecting the release liquid connection of the pressure liquid operated motor to the common return liquid conduit aforesaid, a check valve in the common pressure liquid conduit between the pressure liquid supply conduit and the first liquid pumping unit, and another check valve in the common pressure liquid conduit between the pressure liquid supply conduit and the second liquid pumping unit, each checkvalve being constituted to permit free flow of liquid onlyin the direction from the pumping unit which corresponds to such check valve towards the pressure liquid supply conduit which connects to the liquid operated motor, whereby the refrigerating medium compressing unit may be operated by power derived from the truck power motor during road running of the truck, and whereby said'refrigerating medium compressing unit may beoperated by electric current derived from a source other than the power motor of the truck when saidpower motor is idle.

2. Means as defined in claim 1, wherein the power driven element of the power motor to which the first liquid pumping unit is drivingly connected comprises the 1 Beebe Feb. 8, 1927 Harrington Nov. 14, 1950 

